Grinding mill and material-removing means therefor



Aug, 26, 1924. 1,506,120

H. W. HARDINGE GRINDING MILL AND MATERIAL REMOVING MEANS THEREFOR Filed June 14, 1923 3 SheetS -Sheet 1 vwemtoz War/y 1 1/ f/d/dh e.

H. W. HARDINGE GRINDING MILL AND MATERIAL REMOVING MEANS THEREFOR Filed June 14. 1923 .3 Sheets-Sheet 2 anucufoz 7/0/50 wf/ardhzge. 51 HS al ro'onugs Aug. 26' 9 3924. 1,506,120

H. W. HARDINGE GRINDING MILL AND MATERIAL REMOVING MEANS THEREFOR Filed June 14. 1923 3 Sheets-Sheet 5 I Patented Aug. 26, 1924.

UNITED STATES;

1,50 ,120 ATET OFFICE.

HARRY W. HARDINGE, OF NEW YORK, N. Y., ASSIGNOR TO HARDINGE COMPANY INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF "NEW YORK.

GRINDING MILL AND MATERIAL-REMOVING- MEANS THEREFOR.

Application filed June 14., 1923; Serial No. 645,232.

To all whom it may concern:

Be it known that I, HARRY W. HARDINGE, a citizen of the' United States of America, residing'at New York, county of New York,

5 and State of New York, have invented certain new and useful Improvements in Grinding Mills and Material-Removing Means Therefor, of which the following is a full, clear, and exact description.

This invention relates to grinding mills. More specifically it relates to means for discharging or removing material from such mills, and to means for returning oversize material to such mills.

One of the objects of the invention is to provide novel means for removing material from grinding mills.

Another object is to increase the efticiency of grinding mills, particularly conical mills.

Referring to the drawings which illustrate what I now consider preferred forms of the invention:

Fig. 1 is a sectional, somewhat diagrammatic, elevation illustrating one form of the invention.

Fig. 2 is a fragmentary sectional elevation, similar to Fig. l but illustrating a modification.

' Figs. 3, 4:, 5 and 6 are views similar to Fig. 2 but illustrating further modifications.

While the invention may be applied to other forms of grinding mills, I prefer at present to employ it in connection with the now well known Hardinge conical mill. Referring to Fig. l, the conical mill there shown comprises a drum having a conical inlet portion 10, a cylindrical portion 11, a conical outlet portion 12, an inlet trunnion 13, an outlet trunnion 14, trunnion bearings 15, and a spur gear 16 adapted to be driven by any suitable motor (not shown) to rotate the drum. For simplicity. in illustration, I have not shown any grinding media such as balls, pebbles, rods or the like within the grinding drum, but it will be understood that such grinding media will be provided if desired. The operation of such mills is well understood by those skilled in the art and mav be summarized as follows: Material to be disintegrated or ground is supplied to the drum through the inlet trunnion 13 and is disintegrated within the drum upon rotation of the latter. By virtue of the conical outlet portion 12 the material is automatically classified according to size, the finer particles traveling automatically toward the outlet trunnion 14 whence they are discharged and the coarser particles moving toward the base of the cone 12 until they are disintegrated and reduced in size.

In grinding certain dry ceramic materials, a comparatively fine dust is formed within the grinding drum and, unless removed therefrom, accumulates and forms a cushioning film on the surfaces of the grindmg media, thereby reducing the efiiciency of the mill. In grinding certain other highly hydrated materials, such as gypsum, moisture collects within the grinding drum and, unless removed therefrom, condenses and interferes with efficient operation of the mill. In accordance with the present in vention I provide means for removing dust, or floating particles, or moisture, or combination of the same, from the interior of the grinding drum. One form of such means is shown in Fig. 1 and may be constructed substantially as follows.

A conduit or pipe 17, preferably stationary, extends through the outlet conduit or trunnion 14c of the grinding drum. The conduit 17 is shown flared or funnel-shaped at its inner open end and may be provided with a plurality of perforations 18 in its wall. The conduit 17 constitutes a suction conduit and to that end is connected to the intake side of a suction pump or blower 19 which discharges through a pipe or conduit 20. 1

Any floating particles, such as dust, or

moisture, or mixture of the same are sucked into the inner end of the conduit 17 and ef-' fectively removed from the interior of the grinding drum. It will be understood, of course, that the conduit may be discharged into settling bins, tanks, or other suitable means for retaining material withdrawn from the grinding drum through the conduit 17. It willbe noted that the conduit 17 does not close the outlet conduit or trunnion 14 so that material may be discharged therefrom in the usual way; i. e., by permitting it to drop therefrom by gravity. The suction at the inner end of conduit 17 causes air to be drawn into the grinding drum through that portion of the conduit 14: which surrounds the conduit 17 as well 1 way the floating material (dust, moisture or removal of, oversize; 1.

peripheral perforations 30 0 number as to permit material to escape mixture of the same) is largely prevented from leaving the mill except through the conduit 17 which effectively carries it off to the proper place or apparatus. The conduit or trunnion 14 may be provided with ribs or fins 21, two of which are shown in Fig. 1, which elevate-and then drop the material passing outwardly through the trunnion 14. ThlS enables the inoominrr stream of air, flowing through the 'conduit 14 exteriorly of the conduit 17, to separate the dust, or moisture particles, or both, from the outgoing heavier or coarser particles and to carry the former into the grinding drum whence they are carried outwardly through the conduit 17.

The grinding drum may be provided with a.classifier into which it discharges. Thus, in Fig.1, I have shown a classifier 22 secured to the trunnion 14 and therefore rotatable with the grinding drum. The classifier is shown in the form of a drum provided with peripheral perforations 23 to permit the discharge of the particles of the ground material into the hopper 25. The classifying drum may be provided on its interior with ribs or fins 24 so that any dust, or moisture, or both, carried with the heavier or solid particles from the grinding drum into the classifier drum, will be carried into the grinding drum with the stream ofair passing through the conduit 14 around the conduit 17, this operation being similar to that'of the fins 21. 'It will be noted further that air will be drawn into the classifier 22 through the openings 23 as they rise above the mass of material in the classifier. This action serves to keep the holes 23 open. The classifier 22 may be provided with any suitable means for removing, or permitting the e., material too coarse to pass through the openings 23.

In the modified form of invention shown in'Fig. 2, the elements 112, 114,115, 117, and 121, correspond to-the elements 12, 14,

15, 17, and 21, respectively, of Fig. 1. In,

this form of the invention the conical outlet portion 112 of the mill is such size and through the periphery of the grinding drum as soon as, or substantially as soon as, it is reduced to particles of a predetermined size or degree of fineness. In the operation of this form of the .invention,-dust, or moisture, or mixture of the same, will be sucked into the inner end of the conduit 117 and thereby removed from the grinding drum; fines will drop through the outlet perforations 30 by i gravity; and larger particles will leave the rinding drum through the lower part of t e trunnion 114, dropping therefrom by gravity. As in the case of the openings 23 fprovided with in Fi 1 the incomin air throu h the openings 30 will keep thenrclean and preclassifier 222 rotates in the intake end of the stationary suction conduit 40. The dust or moisture, ornnxture of the same, is drawn by suction from the interior of the drum 212,

through the conduit 214, through the drum 222, through the conduit 35 and thence into and through the conduit 40. The non-floating fines drop from the outlet 214 into the I drum 222 and thence through the. openings 223 by gravity.

In the form of invention shown in F ig. 4,

It will be noted the EEO so formed lying within the trunnion 314 and being surrounded by the bearing 315. The classifier 322 15 shown in g the form of a truncated cone secured at its apex portion to the outlet end of the trunnion 314 so as to rotate with the grinding drum of the mill.

A stationary suction pipe or conduit 340,

terminates slightly within the base of the rotatable classifier 322 and is connected at its other end to the intake of the exhaust fan 319. It will be noted that the conduit 340 slopes up or risesto the fan 319. The classifier 322 is shown provided with a peripheral row of discharge openings 323 adjacent its base, each of said openings be ing of such size as to. permit passage. therethrough by gravity of solid particles of material of the desired size. A plurality of peripheral rows of openings 328 are shown provided in the conical portion of the clas sifier drum 322, each row of such openings 328 being shielded by a corresponding one of a plurality of terrace-forming hoops or bands 339 each secured at itsleft-hand edge to the drum 322. The conduit or .pipe 317 is secured to a spider 350, secured within the trunnion 314, and terminatesat one-end adjacent the intake end of'the suction conduit 340 and at its opposite end within the coni- 'cal outlet 312. The'operation of the mill shown in Fig. 4 is substantially as follows:

Assume that the drum of the grinding mill is being rotated and fed or supplied through its inlet end with material to be disintegrated, and that the fan 319 is being llil operated. Assume further that the material is such that dust-forming particles are formed within the grinding drum, as well as fines of larger size, as the material is subjected to the impact of the grinding media (if these be employed) and abrasion during the passage of the material through the grinding drum. The dust, or finest particles of material, within the grinding drum, particularly within the conical outlet 312, is sucked into the inlet or left-hand end of the conduit 317, then through the conduit 317, and thence into the conduit 340 upwardly, through the fan 319 and outlet 320, and thence into classifying or sorting bins or chambers if these be provided. Any particles which are too heavy to be elevated by the suction draft drop by gravity from the outlet end of conduit 317 into the classifier drum 322, or drop by gravity from the lower end of the conduit 340. Such heavier though fine particles, together with the fines which are discharged through the outlet trunnion 2-114 in the space surrounding the conduit 317, drop by gravity into the rotating classifier drum 322 from which they drop by gravity through the discharge openings 2123. That portion of the heavier though fine material which is discharged into the classifier drum from the grinding mill through the annular space between the interior of the trunnion 314 and the exterior of the conduit 317, drops from one of the hoops or bands to the next in a series of cascades or falls and is swept by the air entering the drum 322 through the openings 328 and the dust or finer flocculent particles effectively removed therefrom. The dust passes up the suction conduit or flue 340. It will therefore be appreciated that two grades of material are removed from the grinding drum. The dust or finest grade passes out through the conduit 320 and the heavier though fine material through the outlet openings 321-). Due to the thorough air-sweeping action the separation or classification of these two grades is effectively accomplished. The actual and relative sizes of the two grades of materials passing out may be controlled within limits by the speed of the grinding drum, the speed of th fan 319, the length of the conduit 817, and other factors.

The form of invention illustrated in Fig. 5 embodies all of the structure, advantages, and features of operation of the form shown in Fig. 4. The elements 412, 414, 415, 417, 419, 420, 422, 423, 428, 439, 440, and 450 of Fig. 5 correspond respectively to the elements 312, 314, 315. 317, 319. 320, .322, 323, 328, 339, 340 and 350 of Fig. 4 and need no further description. In addition the following structure, or means, is provided for automatically returning oversize material to the grinding drum for regrinding. A stationary conduit 441 passes through the conduit 440, drum 422 and conduit 417 ,into the grinding drum. In order to impel or aid in impelling material through this'conduit 441 into the millI provide means for supplying fluid under pressure, preferably gaseous or elastic fluid such as air, to the outer end of the conduit, which has the further advantage of supplying an additional or necessary amount of air. for the suction apparatus. and the further advantage of acting as an agitator for the fines which might otherwise, remain unnecessarily long with the ungronnd material. For this purpose, I have shown a blower or pump 442 having its outlet or pressure side connected to the outer or right hand end of the conduit 441. The latter is shown provided with a hopper 443 adapted to receive oversize material and discharge it into the conduit. Preferably the. lower end of the hopper is provided with a balllo 444 which-serves to deflect the material toward the inner or left-hand or outlet end of the conduit 441, and servcs also to cause an aspirating or entraining action to be exerted upon the material entering from the hopper into the stream of fluid passing through the conduit 441. The conical drum 422 is shown provided at its interior adjacent its base with a periphci'al row of buclcctforming radial lifting vanes 445, which, upon rotation of the drum 422, elevate the oversize material (i. 0. material too large to drop through the openings 423) and discharge it into the. hopper 443 to be discharged into the conduit 441, entrained in the fluid flowing'through the conduit 441, and returned to interior of the grinding drum for regrinding. l have found that in returning the oversize to the mill. the oversize should be projected back from the discharge end of the mill into the main body of. the grinding media lest it gradually collect at or near the outlet and materially interfere with the proper operation of the mill. In this form of mill, the. material discharged or removed from the grinding drum is automatically classified into three grades. The finest or dust-like material is removed from the grinding drum by suction through the opening of the trunnion 414 and conduit 417 (or the former alone if the latter be omitted), then passes through the conduit 440, fan 419 and conduit 420. The heavier though fine particles, as described in connection with Fig. 4, drop by gravity from the trunnion 414 into the classifier drum 422 and leave by gravity through the discharge openings 423. Any oversize which travels with the last mentioned material from the trunnion 414 into the classifier drum 422 is automatically elevated by the vanes 445, dropped into the hopper 443 and returned, through the conduit 441., to the grinding drum for regrinding. Or, if openings 423 be omitted. two sizes alone are produced, i.- e. very fine floatable material and oversize returned for regrinding. By virtue of the hoops or lUU tionhas in some cases entirely obstructed the provided with a flange 317*.

outlet. This objectionable action is substantially prevented by the provision of the inner outlet (17, 117, 317, or 417) which assumes and maintains the same temperature as the interior of the mill. It will be understood further that the inlet endof the grinding drum in each form of the invention as illustrated in the various figures will be closed to a greater or less degree by the material fed or supplied to the mill and that other means for governing the closure of the inlet opening through the inlet trunnion 13 may be provided if desired.

The form of invention shown in Fig. 6 is in most respects similar to that shown in Fig. .4, the same reference numerals being employed to designate the same parts in thetwo figures. In Figs. 6, the conduit 317 has slidably mounted 'thereon'a sleeve 317 By adjusting the conduit 317 longitudinally in its spider 350, or by sliding the sleeve 317 longitudr.

nally on theconduit 317, the flange 317 may he moved from the'positiou shown in Fig. 6 to any one of a number of positions to the left of that position. Obviously, when the parts are in the position shown in Fig. 6, the entire volume of air drawn through the conduit 340 (except slight leakage) passes through the conduit 317. As the flange 317 is moved away from the end of the conduit 3 .0, a proportionately less amount of air passes through the conduit 317. By virtue of these provisions the relative velocities and (plant it ies of air passing inthe various paths may be controlled and adjusted at will. desirable, the conduit 340 may be provided with an opening to atmosphere as shown at 380 and the extent of this opening may be controlled or adjusted by means of a sliding door or closure 381. 1 l

The operation and advantages of the various forms of theinvention will be understood by those skilled in the art, in View of the foregoing disclosure, and need not be further described.

In Figs. 3, 4, 5 and 6 I'have illustrated .various forms of invention in which a classifier is secured to the outlet end of a grinding drum to rotate therewith, the axial opening of the classifier being arranged to discharge fluid-carried material into a suction conduit or uptake. If desirable, a plurality of classifiers may be provided, i. e., the suction conduit may withdraw a stream of material-carrying fluid from the grinding drum through a series of rotating classifiers. Different sizes of floating material would then he collected in the different classifiers.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatuswhich I now con-. sider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the. invention can be carried out by other means. -Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use.

\Vhat I claim is 1. A grinding mill comprising a having an inlet opening and having an outlet opening, and. means for simultaneously passing streams of elastic fluid through said outlet opening in opposite directions, said means comprising a suction conduit extending through said outlet openin 2. A grinding mill having a conical outlet portion for automatically classifying material according to size, and a suction conduit extending through the apex of said outdrum let portion and into the interior of said outlet portion.

1 3. A grinding mill having a conical outlet portion for automatically classifying ma.-v

terial according to size and provided with a discharge opening ,at its apex, and a suction conduit extending through said discharge opening and into the interior of said outlet portion.

at. A' grinding mill comprising in combiuc-ing means for causing a current of elas tic fluid to pass from one of said drums into the other. 5. In combination, a rotatable drum having a conical outlet portion for automatically classifying material according to size, aclassifier secured to said outlet portion at the apex thereof, and a discharge conduit extending through said classifier and into the interior of said outlet portion and having its inlet end within said conical outlet portion.

6. In combination, a rotatable grinding portion and having an outlet. portion, means for withdrawing material from saidoutlet portion by suction, a classifier secured to said drum to rotate therewith and to receive material discharged from said drum, and means for automatically returning oversize material from said classifier to said drum.

'7. In combination, a rotatable grinding drum having an inlet opening and having an outlet opening, means for withdrawing material from said outlet opening by suction, a classifier secured to said drum to rotate therewith and to receive material discharged from said drum, and means for automaticall returning oversize material from said 0 assifier to said drum, through said outlet opening.

8. A grinding mill comprising in combination, a inding drum, a plurality of outdrum having an inlet let conduits for the removal of material from the drum, a classifier for receiving material from said drum, a conduit for returnin oversize to the drum, one of said conduits surrounding the remainder of said conduits.

v9. The combination set forth in claim 8 in which at least one of said outlet. conduits is provided with means for producing asuction' therein and in which the oversize-returning conduit is provided with means for producing fluid pressure therein.

10. In combination, a grinding drum having an outlet conduit and an illet conduit, means for automatically withdrawing fine material from said drum by suction, and means for automatically returning oversize material to said drum under fluid pressure, and means for producing the suction and fluid pressure. 7

11. In combination, a rotatable grinding drum having a trunnion outlet portion, a classifier secured to said drum to rotate therewith and to receive the discharge therefrom, a non-rotating-conveyor tube having an end extending into said trunnion outlet and another end in communication with said classifier, means for supplying fluid under pressure to said tube to impel material therethrough, and means for withdrawing air from the interior of said drum by suction.

' 12. In combination, a rotatable grinding drum having an outlet portion, a rotatable classifying drum into which said grinding drum discharges, means for elevating material in said classifying drum and dropping it by gravity across said classifying drum, means for receiving the oversize material which'drops across said classifying drum and for returning it to said' grinding drum for regrinding, and suction means for causing a stream of elastic fluid to sweep through said classifying drum across the path of descent of the material which drops across said classifying drum.

13. In combination, a rotatable grinding drum, a rotatable classifier for receiving material discharged. from said drum, means for elevatin material in said classifying drum and ropping it by gravity across said classifier, means for receiving comparatively heavy particles which drop across said classifier and returning them to said drum for regrinding, and suction means for causing a stream of elastic fluid to sweep from said drum through said classifier to entrain relatively li ht particles in said drum and in said classi er in the order named.

14. In combination, a grinding drumhaving an outlet conduit and an inlet conduit extending through said outlet conduit, meansfor automatically withdrawing fine material from said drum by suction, means for automatically returning oversize material to said drum through said inlet conduit under fluid producing the suctlon and fluid pressure.

In testimony whereof I hereto afiix my signature.

HARRY W. HARDINGE.

pressure, and means for 

